This emergency elevator system is designed to evacuate people from a high-rise building during an emergency such as a fire or a terrorist attack. This system can simultaneously facilitate an emergency entry for rescue workers and an emergency exit for people in the building while using only the weight of the passengers in the absence of electric power.

This elevator system is comprised of two elevator shafts, each housing an elevator car of the same weight. The elevator cars are interconnected by two hoist cables: one cable is connected to the top of the two elevator cars and is hanging on the pulleys at the upper portion of each elevator shaft, and the other cable is connected to the wall or the bottom portion of the two elevator cars and that cable hangs on the pulley at the lower portion of the elevator shafts. These two elevator cars always move in opposite directions; the heavier car will descend by gravity and the lighter car will ascend as they simultaneously operate. One of the elevator cars will always stay on a designated upper floor and the other one at the ground level. The designated floors with the emergency elevator system are connected to the emergency stairs.

The elevator cars can be made to accommodate 1, 5, 10, 30, 50 passengers or even more. For instance, if 30 passengers, each weighing 90 kilograms (200 pounds), board a car on the 110th floor, the elevator car will descend to the ground like a falling object weighing 2,700 kilograms (6,000 lbs). It will take only 10-15 seconds for that elevator car to reach the ground. At the same time, the other unoccupied elevator car will ascend at the same speed to the 110th floor. Based on the proposed design, if 15 rescue workers (half the number of the descending car) are in the ascending car, the descending elevator car will drop like an object weighing 1,350 kilograms (3,000 lbs) because the ascending elevator car will counterbalance the other 1,350 kilograms (3,000 lbs). The elevator car carrying 15 rescue workers will ascend simultaneously as the other elevator car descends. Moreover, this system can be installed on the interior, exterior or even in the center of a building.

If the World Trade Center buildings involved in the 9/11 attacks had been equipped with this system, it would have saved many lives. In those attacks, because of the fire ignited by the aircraft explosion, the people on the floors above the source of the fire had no chance to escape because the emergency stairs, the only exit at that time, were overwhelmed by fire, smoke, and toxic gas. For one thing, the electric power was disrupted by the attacks. Even if the electric power was still on, the conventional elevators could not have operated through the balls of fire. The people below the fire managed to escape by using the emergency stairs, but the evacuation process was very slow because of the massive crowd of people desperately attempting to escape through the only exit route at the same time. To make it worse, the fire fighters could not climb the stairs as fast as they could have because of the descending crowd. Consequently, the remaining people who were stuck in the stairways and the people on the floors above the fire perished when the building finally collapsed. If only the people had managed to exit the building as quickly as possible, there could have been so many lives saved from this tragedy.

If this emergency elevator system is installed on every 8th floor in a 110-story building, the building will be equipped with a total of 13 emergency elevator systems. In this scenario, it will take about 30 seconds for 30 passengers to get in the upper elevator car and get out of the bottom elevator car; an additional 10-15 seconds for both elevator cars to simultaneously descend and ascend; and an additional 10 seconds for the descending car to reach to the ground after submerging into the liquid reservoir, meanwhile the ascending car slowly reaches its designated floor, locking the car via the automatic locking system to the elevator shaft. If 13 elevator systems are in full operation, it will take about 7 minutes for 3,000 people to evacuate (the same number of people who perished in the 9/11 attack). In the same timeframe of 7 minutes, 1,500 rescue workers can be deployed to the affected floors to contain the fire and rescue people.

In the event of sporadic fires and toxic gas attacks on multiple floors in a high-rise building, the people inside the building will attempt to escape through the emergency stairs. As the evacuees go up or down the stairs, they will reach an emergency elevator system (installed on every 5th, 6th, 7th, or 8th floor depending on the building) that is connected to the stairs.

Because the emergency elevator car is locked to the elevator shaft on its designated floor by an automatic locking system, it will not drop while the passengers are entering or exiting the car as long as the locking system is engaged. Only after the door is closed and the locking lever is manually turned counterclockwise only half way, the automatic locking system will be disengaged. Then the heavier elevator car will descend by the weight of the passengers, and the lighter elevator car on the other side will simultaneously ascend. The fast descending elevator car will hit a liquid reservoir at the bottom of the elevator shaft before slowly coming to a stop at the ground. This liquid reservoir will absorb the incredible impact of the descending car for a safe landing. In the meantime, the other elevator car, which ascended simultaneously at the same speed, will be locked to the elevator shaft at its designated floor. The car will remain locked to the elevator shaft until someone in the car manually disengages the automatic locking system.

As the heavy load of the elevator car hits the liquid reservoir at a fast speed, the liquid will create a spectacular splash as the liquid absorbs such an incredible impact. This liquid splash will wet and cool the elevator car, cables, and the elevator shaft as they have become hot when passing through fire. As a result, the proposed invention will thereby keep the operation of elevators uninterrupted even if the entire building is overwhelmed by fire. As the splashed liquid and the elevator car slowly approach the ground, the liquid overflow at the bottom of the shaft will pass through a hole that is connected to the other elevator shaft. In this way, the liquid will fill the bottom of the other elevator shaft, ready again to receive the next load of elevator car.

The submerged portion of the elevator car works as an air-tight buoy. This air-tight buoy will increase the buoyancy of the elevator car when submerged in the liquid, thereby protecting the elevator car itself as well as the passengers even at a shallow liquid level. As the passengers exit the elevator car after landing and the elevator car becomes lighter again, it will be ready to ascend. Since people will primarily use the emergency elevator system installed on strategically designated floors rather than using the emergency stairs, the emergency stairs will not need to be as wide as they are now. The reduced space and construction cost of the emergency stairs will offset some of the installation cost and space needed for the emergency elevator system.

Moreover, this emergency elevator system has additional benefits. Installed in the elevator cars are a wireless intercom system, TV monitor, and camera that will monitor the inside of the other car and help facilitate communication with each other. The top elevator car will check inside of the bottom car before safely disengaging the locking system. The top car will also check whether the bottom car is empty or how many rescue workers are on board. For instance, if there are 30 evacuees in the top car, about 15 rescue workers may get in the bottom car in order for the system to work. On the other hand, if an equal number of people are in each car, the cars will not move because the weights are counterbalanced. So it would be necessary for the elevator car's operation to add people in the upper car or reduce rescue workers in the bottom car by communicating with each other through the intercom and TV monitor. The intercom and TV monitor will be powered by a rechargeable battery installed on the interior of an elevator car. The rechargeable battery is connected to the generator, which is installed on the exterior of the car. The generator will generate electric power by turning and rolling with the movement of the elevator car in the elevator shaft. If an elevator car remains suspended for a long time, therefore depleted of battery power, cranking the generator handle installed inside the elevator car will generate electric power.

The descending elevator car will be full of people at the outset of an emergency situation, thereby increasing the descending speed. However, as the number of evacuees dwindles, like if only one evacuee enters the car, the descending speed will slow down quite a bit or may not possibly move at all because of the small difference in the weights between the cars. In such a situation, the only remaining passenger may crank the gear handle connected to the gear that is meshed with the perpendicular gear installed on the elevator shaft wall, which will cause the descending elevator car to move. In this case, the remaining passenger needs to crank the gear handle due to the big bulk and heavy weight of the elevator car; but for small and light elevator cars, this action is not necessary since the elevator car will be able to operate by the weight of the remaining evacuee. If there is no descending evacuee but only ascending rescue workers, this emergency elevator system will use one of the following means: As the first means, the rescue workers may crank the gear handle inside the elevator car, enabling the elevator car to ascend. As an alternate means, a third person may crank the pulley handle located outside the elevator shaft to lift the elevator car. In both cases, however, the speed of the elevator car will be slow and difficult to lift many people. As the third means, a fuel-operated motor, such as a car's motor, can be connected to the pulley, operating it so that the rescue workers may move up much faster and safer than climbing the emergency stairs.

Addition

1. Assuming an elevator car carrying 30 passengers hits the liquid reservoir at the bottom of the shaft from the top of a 110-story building (413 m) , how deep should the reservoir be to absorb the impact of the car to guarantee a safe landing of the passengers and the elevator car? If an elevator car carrying 30 passengers is dropped to an open lake from the same height, for the sake of argument, the lake should be around 50 meters deep to safely absorb the impact. However, if an elevator car carrying 30 passengers travel through a shaft inside a building as illustrated in the proposed invention, a water level as deep as 1/5 (or 10 meters) of the open lake will suffice. The reason is when an elevator car hits an open lake, the lake water will absorb the impact while being splashed in all directions thereby creating less resistance. But the liquid reservoir at the bottom of the elevator shaft in our system will have no escape route as it splashes thus creating much more resistance. (The liquid will splash through a small gap between the elevator shaft wall and the elevator car, and the splashing water will wet and cool the interior of the elevator shaft, elevator car, and cables). In other words, because the liquid cannot escape from a confined space, it will offer a tremendous resistance to the impact created by the descending elevator car. The elevator car will consequently slow down by the resistance, protecting the passengers and the elevator car even if the liquid level is relatively low. As an analogy, if the air hole at the end of a bicycle hand pump tube is wide open, the piston can be pushed down easily without resistance. When you pump harder, the piston can be damaged by the impact. If the air hole is blocked, the piston can not be pushed down no matter how much power is exerted. If the hole is only partially open, the air pump piston will be pushed down gently and safely, even when you pump harder. It is the same principle.